It's one of the most often questions asked by readers contemplating a purchase of the 27-inch 'late 2012' iMac -- is the optional GeForce GTX 680MX worth it?

In "Take One,", we examined the specs and shared a few performance graphs. Our quest to answer the question continues with two new OpenGL benchmarks: Heaven 4.0 and Valley 1.0.

Unigine has recently updated the Heaven Benchmark from version 3.0 to version 4.0. It uses the same 26 scenes of a village, a ship, and floating islands using advanced ambient occlusion, volumetric clouds, and various lighting conditions with refraction. This version adds two presets to help standardize comparison testing: Basic and Extreme.

We used Extreme preset for our testing which uses 1600x900 windowed resolution with 8x Anti-aliasing, Ultra Quality for Shaders and Textures, Extreme Tessellation, and with Occlusion, Refraction, and Volumetric Shadows enabled. We posted graphs with AVERAGE and MINIMUM frames per second. (LONGER means FASTER.)

Unigine has added a new GPU benchmark called Valley. It "flies" through forest-covered valley surrounded by vast mountains. It amazes with its scale from a birdŐs-eye view of 64 million meters of extremely detailed terrain down to every leaf and flower petal. It features advanced visual technologies: dynamic sky, volumetric clouds, sun shafts, DOF, ambient occlusion.

It provides three presets to help standardize comparison testing: Basic, Extreme, and Extreme HD. We used Extreme preset: 1600x900 windowed resolution with 8x Anti-aliasing, Ultra Quality for Shaders and Textures, and with Occlusion, Refraction, and Volumetric Shadows enabled. We posted AVERAGE and MINIMUM frames per second. (LONGER means FASTER.)

PERFORMANCE INSIGHTSBoth Heaven and Valley are a 'pure' GPU tests in that they maximize GPU load (according to OpenGL Driver Monitor) while the CPU only requires one core averaging a 50% load -- when running the Extreme preset. They both consumed almost 900MB of the video memory on our iMac test unit when running the Extreme preset.

In the case of Heaven 4.0, the GeForce GTX 680MX GPU averaged 21.8% faster FPS than the 675MX. In the case of Valley, the 680MX averaged 10.6% faster. Considering the $150 for the 680MX only adds 5.7% to 7.5% to the price of the 27" iMac (depending on the configuration), I maintain it is a bargain upgrade.

Also, the added video memory (2G vs 1G) comes in handy not only for games like Civilization V but also for pro apps like Aperture (as when running Noise Ninja).

If your budget is tight, you can offset the price of the GTX 680MX by ordering your 27" iMac with less memory or without AppleCare. Really? Yes, because you can add both later. You can NOT add a better GPU later.

SPECIAL THANKS...
to Menta, a remote mad scientist in France, for the GTX 675MX test results.